An explosion ripped through a military convoy in Pakistan on January 19.

Pakistani officials say at least 20 soldiers were killed and 30 wounded in the attack at a military base in the town of Bannu in the North Waziristan tribal region.

The Taliban later claimed it was behind the attack and vowed more.

It was unclear what caused the explosion. AP quotes police as saying a bomb had been planted in a vehicle hired by the paramilitary Frontier Corps. But Reuters quotes other officials as saying it may have been a roadside bomb.

North Waziristan is considered a safe haven for Taliban and Al-Qaeda linked militants. Pakistani troop convoys often are hit by roadside bombs, but blasts inside a compound are rare.